Channel quality reporting for different types of subframes

ABSTRACT

A method for determining channel quality estimates of two or more types of subframes, such as clean and unclean subframes, may be applicable to both legacy and newer user equipment. A first base station affects a channel quality measurement by either transmitting dummy signals over designed tones that correspond to a second base station, or by puncturing transmissions during designated tones that correspond to the second base station.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.13/163,595, entitled “Channel Quality Reporting for Different Types ofSubframes” filed on Jun. 17, 2011, currently pending, which claims thebenefit under 35 U.S.C. §119(e) to U.S. Provisional Patent ApplicationNo. 61/356,346 entitled “Channel Quality Reporting for Clean and UncleanSubframes,” filed on Jun. 18, 2010, the disclosures of which areexpressly incorporated by reference herein in their entireties.

BACKGROUND

1. Field

Aspects of the present disclosure relate generally to wirelesscommunication systems, and more particularly to reporting channelquality in wireless communications systems.

2. Background

Wireless communication networks are widely deployed to provide variouscommunication services such as voice, video, packet data, messaging,broadcast, etc. These wireless networks may be multiple-access networkscapable of supporting multiple users by sharing the available networkresources. Examples of such multiple-access networks include CodeDivision Multiple Access (CDMA) networks, Time Division Multiple Access(TDMA) networks, Frequency Division Multiple Access (FDMA) networks,Orthogonal FDMA (OFDMA) networks, and Single-Carrier FDMA (SC-FDMA)networks.

A wireless communication network may include a number of base stationsthat can support communication for a number of user equipments (UEs). AUE may communicate with a base station via the downlink and uplink. Thedownlink (or forward link) refers to the communication link from thebase station to the UE, and the uplink (or reverse link) refers to thecommunication link from the UE to the base station.

A base station may transmit data and control information on the downlinkto a UE and/or may receive data and control information on the uplinkfrom the UE. On the downlink, a transmission from the base station mayencounter interference due to transmissions from neighbor base stationsor from other wireless radio frequency (RF) transmitters. On the uplink,a transmission from the UE may encounter interference from uplinktransmissions of other UEs communicating with the neighbor base stationsor from other wireless RF transmitters. This interference may degradeperformance on both the downlink and uplink.

As the demand for mobile broadband access continues to increase, thepossibilities of interference and congested networks grows with more UEsaccessing the long-range wireless communication networks and moreshort-range wireless systems being deployed in communities. Research anddevelopment continue to advance the UMTS technologies not only to meetthe growing demand for mobile broadband access, but to advance andenhance the user experience with mobile communications.

SUMMARY

One aspect discloses reporting channel quality estimations of two ormore types of subframes, such as clean and unclean subframes that areapplicable to both legacy and newer user equipment. A first base stationaffects a channel quality measurement by either transmitting dummysignals over designed tones that correspond to a second base station, orby puncturing transmissions during designated tones that correspond tothe second base station.

In one aspect, a method for channel quality estimation by a first basestation in a wireless network, is disclosed. The method includesdetermining a subframe in which a user equipment (UE) served by a secondbase station will perform a channel quality measurement. The channelquality measurement is affected by either transmitting dummy signalsover designated tones corresponding to the second base station on afirst selected subband during the subframe or by puncturingtransmissions during designated tones corresponding to the second basestation over a second selected subband during the subframe.

Another aspect discloses a method for channel quality estimation in awireless network and includes indicating, to a user equipment (UE), toperform a plurality of channel quality measurements for at least twosubbands in a subframe. A first channel quality report including a firstchannel quality measurement of a first subband and a second channelquality report including a second channel quality measurement of asecond subband are received from the UE. Separate channel qualitymeasurements for a first subframe type and a second subframe type aredetermined based on the first and second reports.

Another aspect discloses an apparatus including means for determining asubframe in which a user equipment (UE) served by a second base stationwill perform a channel quality measurement. Also included is means foraffecting the channel quality measurement where the means includestransmitting dummy signals over designated tones corresponding to thesecond base station on a first selected subband during the subframe orthe means includes puncturing transmissions during designated tonescorresponding to the second base station over a second selected subbandduring the subframe.

In another aspect, an apparatus for wireless communication is disclosedand includes means for indicating, to a user equipment (UE), to performa plurality of channel quality measurements for at least two subbands ina subframe. Also included is a means for receiving a first channelquality report and a second channel quality report from the UE. Thefirst channel quality report includes a first channel qualitymeasurement of a first subband and the second channel quality reportincludes a second channel quality measurement of a second subband. Alsoincluded is a means for determining separate channel qualitymeasurements for a first subframe type and a second subframe type basedon the first and second reports.

A computer program product for wireless communications in a wirelessnetwork is also disclosed. The computer readable medium has program coderecorded thereon which, when executed by the processor(s), causes theprocessor(s) to perform operations of determining a subframe in which auser equipment (UE) served by a second base station will perform achannel quality measurement. The program code also causes theprocessor(s) to affect the channel quality measurement. The channelquality measurement may be affected by transmitting dummy signals overdesignated tones corresponding to the second base station on a firstselected subband during the subframe, or by puncturing transmissionsduring designated tones corresponding to the second base station over asecond selected subband during the subframe.

A computer program product for wireless communications in a wirelessnetwork is also disclosed. The computer readable medium has program coderecorded thereon which, when executed by the processor(s), causes theprocessor(s) to perform operations of indicating, to a user equipment(UE), to perform a plurality of channel quality measurements for atleast two subbands in a subframe. The program code also causes theprocessor(s) to receive a first channel quality report and a secondchannel quality report from the UE. The first channel quality reportincludes a first channel quality measurement of a first subband and thesecond channel quality report includes a second channel qualitymeasurement of a second subband. The program code also causes theprocessor(s) to determine separate channel quality measurements for afirst subframe type and a second subframe type based on the first andsecond reports.

Another aspect discloses wireless communication having a memory and atleast one processor coupled to the memory. The processor(s) isconfigured to determine a subframe in which a user equipment (UE) servedby a second base station will perform a channel quality measurement. Theprocessor(s) is also configured to affect the channel qualitymeasurement by transmitting dummy signals over designated tonescorresponding to the second base station on a first selected subbandduring the subframe, or by puncturing transmissions during designatedtones corresponding to the second base station over a second selectedsubband during the subframe.

In another aspect, wireless communication having a memory and at leastone processor coupled to the memory is disclosed. The processor(s) isconfigured to indicate, to a user equipment (UE), to perform a pluralityof channel quality measurements for at least two subbands in a subframe.Additionally, the processor(s) is configured to receive, from the UE, afirst channel quality report including a first channel qualitymeasurement of a first subband and a second channel quality reportincluding a second channel quality measurement of a second subband.Further, the processor(s) is configured to determine separate channelquality measurements for a first subframe type and a second subframetype based on the first and second reports.

This has outlined, rather broadly, the features and technical advantagesof the present disclosure in order that the detailed description thatfollows may be better understood. Additional features and advantages ofthe disclosure will be described below. It should be appreciated bythose skilled in the art that this disclosure may be readily utilized asa basis for modifying or designing other structures for carrying out thesame purposes of the present disclosure. It should also be realized bythose skilled in the art that such equivalent constructions do notdepart from the teachings of the disclosure as set forth in the appendedclaims. The novel features, which are believed to be characteristic ofthe disclosure, both as to its organization and method of operation,together with further objects and advantages, will be better understoodfrom the following description when considered in connection with theaccompanying figures. It is to be expressly understood, however, thateach of the figures is provided for the purpose of illustration anddescription only and is not intended as a definition of the limits ofthe present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The features, nature, and advantages of the present disclosure willbecome more apparent from the detailed description set forth below whentaken in conjunction with the drawings in which like referencecharacters identify correspondingly throughout.

FIG. 1 is a block diagram conceptually illustrating an example of atelecommunications system.

FIG. 2 is a diagram conceptually illustrating an example of a downlinkframe structure in a telecommunications system.

FIG. 3 is a block diagram conceptually illustrating an example framestructure in uplink communications.

FIG. 4 is a block diagram conceptually illustrating a design of a basestation/eNodeB and a UE configured according to one aspect of thepresent disclosure.

FIG. 5 is a block diagram conceptually illustrating adaptive resourcepartitioning in a heterogeneous network according to one aspect of thedisclosure.

FIG. 6 is a block diagram illustrating the channel quality indicator(CQI) reporting period according to one aspect of the presentdisclosure.

FIGS. 7A-7C are block diagrams illustrating channel quality indexreporting for different types of subframes.

FIG. 8A is a block diagram conceptually illustrating transmitting dummydata to simulated unclean subframes.

FIG. 8B is a block diagram conceptually illustrating puncturing subbandsto simulate.

DETAILED DESCRIPTION

The detailed description set forth below, in connection with theappended drawings, is intended as a description of variousconfigurations and is not intended to represent the only configurationsin which the concepts described herein may be practiced. The detaileddescription includes specific details for the purpose of providing athorough understanding of the various concepts. However, it will beapparent to those skilled in the art that these concepts may bepracticed without these specific details. In some instances, well-knownstructures and components are shown in block diagram form in order toavoid obscuring such concepts.

The techniques described herein may be used for various wirelesscommunication networks such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA andother networks. The terms “network” and “system” are often usedinterchangeably. A CDMA network may implement a radio technology, suchas Universal Terrestrial Radio Access (UTRA), TelecommunicationsIndustry Association's (TIA's) CDMA2000®, and the like. The UTRAtechnology includes Wideband CDMA (WCDMA) and other variants of CDMA.The CDMA2000® technology includes the IS-2000, IS-95 and IS-856standards from the Electronics Industry Alliance (EIA) and TIA. A TDMAnetwork may implement a radio technology, such as Global System forMobile Communications (GSM). An OFDMA network may implement a radiotechnology, such as Evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB),IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDMA, andthe like. The UTRA and E-UTRA technologies are part of Universal MobileTelecommunication System (UMTS). 3GPP Long Term Evolution (LTE) andLTE-Advanced (LTE-A) are newer releases of the UMTS that use E-UTRA.UTRA, E-UTRA, UMTS, LTE, LTE-A and GSM are described in documents froman organization called the “3rd Generation Partnership Project” (3GPP).CDMA2000® and UMB are described in documents from an organization calledthe “3rd Generation Partnership Project 2” (3GPP2). The techniquesdescribed herein may be used for the wireless networks and radio accesstechnologies mentioned above, as well as other wireless networks andradio access technologies. For clarity, certain aspects of thetechniques are described below for LTE or LTE-A (together referred to inthe alternative as “LTE/-A”) and use such LTE/-A terminology in much ofthe description below.

FIG. 1 shows a wireless communication network 100, which may be an LTE-Anetwork, in which channel quality reporting for clean and uncleansubframes may be implemented. The wireless network 100 includes a numberof evolved node Bs (eNodeBs) 110 and other network entities. An eNodeBmay be a station that communicates with the UEs and may also be referredto as a base station, a node B, an access point, and the like. EacheNodeB 110 may provide communication coverage for a particulargeographic area. In 3GPP, the term “cell” can refer to this particulargeographic coverage area of an eNodeB and/or an eNodeB subsystem servingthe coverage area, depending on the context in which the term is used.

An eNodeB may provide communication coverage for a macro cell, a picocell, a femto cell, and/or other types of cell. A macro cell generallycovers a relatively large geographic area (e.g., several kilometers inradius) and may allow unrestricted access by UEs with servicesubscriptions with the network provider. A pico cell would generallycover a relatively smaller geographic area and may allow unrestrictedaccess by UEs with service subscriptions with the network provider. Afemto cell would also generally cover a relatively small geographic area(e.g., a home) and, in addition to unrestricted access, may also providerestricted access by UEs having an association with the femto cell(e.g., UEs in a closed subscriber group (CSG), UEs for users in thehome, and the like). An eNodeB for a macro cell may be referred to as amacro eNodeB. An eNodeB for a pico cell may be referred to as a picoeNodeB. And, an eNodeB for a femto cell may be referred to as a femtoeNodeB or a home eNodeB. In the example shown in FIG. 1, the eNodeBs 110a, 110 b and 110 c are macro eNodeBs for the macro cells 102 a, 102 band 102 c, respectively. The eNodeB 110 x is a pico eNodeB for a picocell 102 x. And, the eNodeBs 110 y and 110 z are femto eNodeBs for thefemto cells 102 y and 102 z, respectively. An eNodeB may support one ormultiple (e.g., two, three, four, and the like) cells.

The wireless network 100 may also include relay stations. A relaystation is a station that receives a transmission of data and/or otherinformation from an upstream station (e.g., an eNodeB, UE, etc.) andsends a transmission of the data and/or other information to adownstream station (e.g., a UE or an eNodeB). A relay station may alsobe a UE that relays transmissions for other UEs. In the example shown inFIG. 1, a relay station 110 r may communicate with the eNodeB 110 a anda UE 120 r in order to facilitate communication between the eNodeB 110 aand the UE 120 r. A relay station may also be referred to as a relayeNodeB, a relay, etc.

The wireless network 100 may be a heterogeneous network that includeseNodeBs of different types, e.g., macro eNodeBs, pico eNodeBs, femtoeNodeBs, relays, etc. These different types of eNodeBs may havedifferent transmit power levels, different coverage areas, and differentimpact on interference in the wireless network 100. For example, macroeNodeBs may have a high transmit power level (e.g., 20 Watts) whereaspico eNodeBs, femto eNodeBs and relays may have a lower transmit powerlevel (e.g., 1 Watt).

The wireless network 100 supports a synchronous operation where theeNodeBs have similar frame timing, and transmissions from differenteNodeBs may be approximately aligned in time. In one aspect, thewireless network 100 may support frequency division duplex (FDD) modesof operation.

A network controller 130 may couple to a set of eNodeBs 110 and providecoordination and control for these eNodeBs 110. The network controller130 may communicate with the eNodeBs 110 via a backhaul. The eNodeBs 110may also communicate with one another, e.g., directly or indirectly viaa wireless backhaul or a wireline backhaul.

The UEs 120 are dispersed throughout the wireless network 100, and eachUE may be stationary or mobile. A UE may also be referred to as aterminal, a mobile station, a subscriber unit, a station, or the like. AUE may be a cellular phone, a personal digital assistant (PDA), awireless modem, a wireless communication device, a handheld device, alaptop computer, a cordless phone, a wireless local loop (WLL) station,a tablet, or the like. A UE may be able to communicate with macroeNodeBs, pico eNodeBs, femto eNodeBs, relays, and the like. In FIG. 1, asolid line with double arrows indicates desired transmissions between aUE and a serving eNodeB, which is an eNodeB designated to serve the UEon the downlink and/or uplink. A dashed line with double arrowsindicates interfering transmissions between a UE and an eNodeB.

LTE utilizes orthogonal frequency division multiplexing (OFDM) on thedownlink and single-carrier frequency division multiplexing (SC-FDM) onthe uplink. OFDM and SC-FDM partition the system bandwidth into multiple(K) orthogonal subcarriers, which are also commonly referred to astones, bins, or the like. Each subcarrier may be modulated with data. Ingeneral, modulation symbols are sent in the frequency domain with OFDMand in the time domain with SC-FDM. The spacing between adjacentsubcarriers may be fixed, and the total number of subcarriers (K) may bedependent on the system bandwidth.

FIG. 2 shows a downlink FDD frame structure used in LTE in which channelquality reporting for clean and unclean subframes may be implemented.The transmission timeline for the downlink may be partitioned into unitsof radio frames. Each radio frame may have a predetermined duration(e.g., 10 milliseconds (ms)) and may be partitioned into 10 subframeswith indices of 0 through 9. Each subframe may include two slots. Eachradio frame may thus include 20 slots with indices of 0 through 19. Eachslot may include L symbol periods, e.g., 7 symbol periods for a normalcyclic prefix (as shown in FIG. 2) or 6 symbol periods for an extendedcyclic prefix. The 2L symbol periods in each subframe may be assignedindices of 0 through 2L-1. The available time frequency resources may bepartitioned into resource blocks. Each resource block may cover Nsubcarriers (e.g., 12 subcarriers) in one slot.

In LTE, an eNodeB may send a primary synchronization signal (PSC or PSS)and a secondary synchronization signal (SSC or SSS) for each cell in theeNodeB. For FDD mode of operation, the primary and secondarysynchronization signals may be sent in symbol periods 6 and 5,respectively, in each of subframes 0 and 5 of each radio frame with thenormal cyclic prefix, as shown in FIG. 2. The synchronization signalsmay be used by UEs for cell detection and acquisition. For FDD mode ofoperation, the eNodeB may send a Physical Broadcast Channel (PBCH) insymbol periods 0 to 3 in slot 1 of subframe 0. The PBCH may carrycertain system information.

The eNodeB may send a Physical Control Format Indicator Channel (PCFICH)in the first symbol period of each subframe, as seen in FIG. 2. ThePCFICH may convey the number of symbol periods (M) used for controlchannels, where M may be equal to 1, 2 or 3 and may change from subframeto subframe. M may also be equal to 4 for a small system bandwidth,e.g., with less than 10 resource blocks. In the example shown in FIG. 2,M=3. The eNodeB may send a Physical HARQ Indicator Channel (PHICH) and aPhysical Downlink Control Channel (PDCCH) in the first M symbol periodsof each subframe. The PDCCH and PHICH are also included in the firstthree symbol periods in the example shown in FIG. 2. The PHICH may carryinformation to support hybrid automatic retransmission (HARQ). The PDCCHmay carry information on uplink and downlink resource allocation for UEsand power control information for uplink channels. The eNodeB may send aPhysical Downlink Shared Channel (PDSCH) in the remaining symbol periodsof each subframe. The PDSCH may carry data for UEs scheduled for datatransmission on the downlink.

The eNodeB may send the PSC, SSC and PBCH in the center 1.08 MHz of thesystem bandwidth used by the eNodeB. The eNodeB may send the PCFICH andPHICH across the entire system bandwidth in each symbol period in whichthese channels are sent. The eNodeB may send the PDCCH to groups of UEsin certain portions of the system bandwidth. The eNodeB may send thePDSCH to groups of UEs in specific portions of the system bandwidth. TheeNodeB may send the PSC, SSC, PBCH, PCFICH and PHICH in a broadcastmanner to all UEs, may send the PDCCH in a unicast manner to specificUEs, and may also send the PDSCH in a unicast manner to specific UEs.

A number of resource elements may be available in each symbol period.Each resource element may cover one subcarrier in one symbol period andmay be used to send one modulation symbol, which may be a real orcomplex value. For symbols that are used for control channels, theresource elements not used for a reference signal in each symbol periodmay be arranged into resource element groups (REGs). Each REG mayinclude four resource elements in one symbol period.

A UE may know the specific REGs used for the PHICH and the PCFICH. TheUE may search different combinations of REGs for the PDCCH. The numberof combinations to search is typically less than the number of allowedcombinations for all UEs in the PDCCH. An eNodeB may send the PDCCH tothe UE in any of the combinations that the UE will search.

A UE may be within the coverage of multiple eNodeBs. One of theseeNodeBs may be selected to serve the UE. The serving eNodeB may beselected based on various criteria such as received power, path loss,signal-to-noise ratio (SNR), etc.

FIG. 3 is a block diagram conceptually illustrating an exemplary FDD andTDD (non-special subframe only) subframe structure in uplink long termevolution (LTE) communications. The available resource blocks (RBs) forthe uplink may be partitioned into a data section and a control section.The control section may be formed at the two edges of the systembandwidth and may have a configurable size. The resource blocks in thecontrol section may be assigned to UEs for transmission of controlinformation. The data section may include all resource blocks notincluded in the control section. The design in FIG. 3 results in thedata section including contiguous subcarriers, which may allow a singleUE to be assigned all of the contiguous subcarriers in the data section.

A UE may be assigned resource blocks in the control section to transmitcontrol information to an eNodeB. The UE may also be assigned resourceblocks in the data section to transmit data to the eNodeB. The UE maytransmit control information in a Physical Uplink Control Channel(PUCCH) on the assigned resource blocks in the control section. The UEmay transmit only data or both data and control information in aPhysical Uplink Shared Channel (PUSCH) on the assigned resource blocksin the data section. An uplink transmission may span both slots of asubframe and may hop across frequency as shown in FIG. 3. According toone aspect, in relaxed single carrier operation, parallel channels maybe transmitted on the UL resources. For example, a control and a datachannel, parallel control channels, and parallel data channels may betransmitted by a UE.

FIG. 4 shows a block diagram of a design of a base station/eNodeB 110and a UE 120, in which channel quality reporting for clean and uncleansubframes may be implemented. The eNodeB 110 and UE 120 may be one ofthe base stations/eNodeBs and one of the UEs in FIG. 1. The base station110 may be the macro eNodeB 110 c in FIG. 1, and the UE 120 may be theUE 120 y. The base station 110 may also be a base station of some othertype. The base station 110 may be equipped with antennas 434 a through434 t, and the UE 120 may be equipped with antennas 452 a through 452 r.

At the base station 110, a transmit processor 420 may receive data froma data source 412 and control information from a controller/processor440. The control information may be for the PBCH, PCFICH, PHICH, PDCCH,etc. The data may be for the PDSCH, etc. The processor 420 may process(e.g., encode and symbol map) the data and control information to obtaindata symbols and control symbols, respectively. The processor 420 mayalso generate reference symbols, e.g., for the PSS, SSS, andcell-specific reference signal. A transmit (TX) multiple-inputmultiple-output (MIMO) processor 430 may perform spatial processing(e.g., precoding) on the data symbols, the control symbols, and/or thereference symbols, if applicable, and may provide output symbol streamsto the modulators (MODs) 432 a through 432 t. Each modulator 432 mayprocess a respective output symbol stream (e.g., for OFDM, etc.) toobtain an output sample stream. Each modulator 432 may further process(e.g., convert to analog, amplify, filter, and upconvert) the outputsample stream to obtain a downlink signal. Downlink signals frommodulators 432 a through 432 t may be transmitted via the antennas 434 athrough 434 t, respectively.

At the UE 120, the antennas 452 a through 452 r may receive the downlinksignals from the base station 110 and may provide received signals tothe demodulators (DEMODs) 454 a through 454 r, respectively. Eachdemodulator 454 may condition (e.g., filter, amplify, downconvert, anddigitize) a respective received signal to obtain input samples. Eachdemodulator 454 may further process the input samples (e.g., for OFDM,etc.) to obtain received symbols. A MIMO detector 456 may obtainreceived symbols from all the demodulators 454 a through 454 r, performMIMO detection on the received symbols if applicable, and providedetected symbols. A receive processor 458 may process (e.g., demodulate,deinterleave, and decode) the detected symbols, provide decoded data forthe UE 120 to a data sink 460, and provide decoded control informationto a controller/processor 480.

On the uplink, at the UE 120, a transmit processor 464 may receive andprocess data (e.g., for the PUSCH) from a data source 462 and controlinformation (e.g., for the PUCCH) from the controller/processor 480. Theprocessor 464 may also generate reference symbols for a referencesignal. The symbols from the transmit processor 464 may be precoded by aTX MIMO processor 466 if applicable, further processed by the modulators454 a through 454 r (e.g., for SC-FDM, etc.), and transmitted to thebase station 110. At the base station 110, the uplink signals from theUE 120 may be received by the antennas 434, processed by thedemodulators 432, detected by a MIMO detector 436 if applicable, andfurther processed by a receive processor 438 to obtain decoded data andcontrol information sent by the UE 120. The processor 438 may providethe decoded data to a data sink 439 and the decoded control informationto the controller/processor 440. The base station 110 can send messagesto other base stations, for example, over an X2 interface 441.Additionally, the memory 442 may include a subframeidentification/negotiation module 446. The memory 442 may also include aCQI management module 448.

The controllers/processors 440 and 480 may direct the operation at thebase station 110 and the UE 120, respectively. The processor 440 and/orother processors and modules at the base station 110 may perform ordirect the execution of various processes for the techniques describedherein. The processor 480 and/or other processors and modules at the UE120 may also perform or direct the execution of the functional blocksillustrated in use method flow chart FIGS. 7A and 7B, and/or otherprocesses for the techniques described herein. The memories 442 and 482may store data and program codes for the base station 110 and the UE120, respectively. A scheduler 444 may schedule UEs for datatransmission on the downlink and/or uplink.

A UE may be within the coverage of multiple eNodeBs and one of theseeNodeBs may be selected to serve the UE. The serving eNodeB may beselected based on various criteria such as, but not limited to, receivedpower, path loss, signal to noise ratio (SNR), etc. In deployments ofheterogeneous networks, such as the wireless network 100, a UE mayoperate in a dominant interference scenario in which the UE may observehigh interference from one or more interfering eNodeBs.

A dominant interference scenario may occur due to restrictedassociation. For example, in FIG. 1, the UE 120 y may be close to thefemto eNodeB 110 y and may have high received power for the eNodeB 110y. However, the UE 120 y may not be able to access the femto eNodeB 110y due to restricted association and may then connect to the macro eNodeB110 c (as shown in FIG. 1) or to the femto eNodeB 110 z also with lowerreceived power (not shown in FIG. 1). The UE 120 y may then observe highinterference from the femto eNodeB 110 y on the downlink and may alsocause high interference to the eNodeB 110 y on the uplink. Coordinatedinterference management may be used to allow the eNodeB 110 c and thefemto eNodeB 110 y to communicate over the backhaul to negotiateresources. In the negotiation, the femto eNodeB 110 y agrees to ceasetransmission on one of its channel resources, such that the UE 120 ywill not experience as much interference from the femto eNodeB 110 y asit communicates with the eNodeB 110 c over that same channel.

With range extension enabled in a wireless network, such as the wirelessnetwork 100, in order for UEs to obtain service from a lower power basestation (i.e., a pico or femto base station) in the presence of a macrobase station with stronger downlink signal strength, or for the UEs toobtain service from a macro base station in the presence of a stronglyinterfering signal from a femto base station to which the UE is notauthorized to connect, an enhanced inter-cell interference coordination(eICIC) may be used to coordinate the interfering base station giving upsome resources in order to enable control and data transmissions betweenthe UE and the serving base station. When a network supports eICIC, thebase stations negotiate with each other to coordinate resources in orderto reduce/eliminate interference by the interfering cell giving up partof its resources. With this, a UE can access the serving cell even withsevere interference by using the resources yielded by the interferingcell.

A coverage lapse within a macro cell may exist when a femto cell with aclosed access mode, in which only member femto UEs may access the cell,lies within the coverage area of the macro cell. By making this femtocell give up some of its resources, the UE within the femto cellcoverage area may access its serving macro cell by using the resourcesyielded by the femto cell. In a radio access system using OFDM such asE-UTRAN, these yielded resources may be time-based, frequency-based, ora combination of both. When the yielded resources are time-based, theinterfering cell refrains from using some of its accessible subframes inthe time domain. When these resources are frequency-based, theinterfering cell does not use some of its accessible subcarriers in thefrequency domain. When the yielded resources are a combination of bothfrequency and time, the interfering cell does not use the resourcesdefined by frequency and time.

Heterogeneous networks may use inter-cell interference coordination(ICIC) to reduce interference from cells in co-channel deployment. OneICIC mechanism is time division multiplexing (TDM) partitioning. In TDMpartitioning, subframes are assigned to certain eNodeBs. In subframesassigned to a first eNodeB, neighbor eNodeBs do not transmit. Thus,interference experienced by a UE served by the first eNodeB is reduced.Subframe assignment may be performed on both the uplink and downlinkchannels.

For example, subframes may be allocated between three classes ofsubframes: protected subframes (U subframes), prohibited subframes (Nsubframes), and common subframes (C subframes). Protected subframes areassigned to a first eNodeB for use exclusively by the first eNodeB.Protected subframes may also be referred to as “clean” subframes basedon the lack of interference from neighboring eNodeBs. Prohibitedsubframes are subframes assigned to a neighbor eNodeB, and the firsteNodeB is prohibited from transmitting data during the prohibitedsubframes. For example, a prohibited subframe of the first eNodeB maycorrespond to a protected subframe of a second interfering eNodeB. Thus,the first eNodeB is the only eNodeB transmitting data during the firsteNodeB's protected subframe. Common subframes may be used for datatransmission by multiple eNodeBs. Common subframes may also be referredto as “unclean” subframes because of the possibility of interferencefrom other eNodeBs.

At least one protected subframe is statically assigned per period. Insome cases only one protected subframe is statically assigned. Forexample, if a period is 8 milliseconds, one protected subframe may bestatically assigned to an eNodeB during every 8 milliseconds. Othersubframes may be dynamically allocated.

Adaptive resource partitioning information (ARPI) allows thenon-statically assigned subframes to be dynamically allocated. Any ofprotected, prohibited, or common subframes may be dynamically allocated(AU, AN, AC subframes, respectively). The dynamic assignments may changequickly, such as, for example, every one hundred milliseconds or less.

Heterogeneous networks may have eNodeBs of different power classes. Forexample, three power classes may be defined, in decreasing power class,as macro eNodeBs, pico eNodeBs, and femto eNodeBs. When macro eNodeBs,pico eNodeBs, and femto eNodeBs are in a co-channel deployment, thepower spectral density (PSD) of the macro eNodeB (aggressor eNodeB) maybe larger than the power spectral density of the pico eNodeB and thefemto eNodeB (victim eNodeBs) creating large amounts of interferencewith the pico eNodeB and the femto eNodeB. Protected subframes may beused to reduce or minimize interference with the pico eNodeBs and femtoeNodeBs. That is, a protected subframe may be scheduled for the victimeNodeB to correspond with a prohibited subframe on the aggressor eNodeB.

FIG. 5 is a block diagram illustrating TDM partitioning in aheterogeneous network in which channel quality reporting for clean andunclean subframes may be implemented. A first row of blocks illustratesubframe assignments for a femto eNodeB, and a second row of blocksillustrate subframe assignments for a macro eNodeB. Each of the eNodeBshas a static protected subframe during which the other eNodeB has astatic prohibited subframe. For example, the femto eNodeB has aprotected subframe (U subframe) in subframe 0 corresponding to aprohibited subframe (N subframe) in subframe 0. Likewise, the macroeNodeB has a protected subframe (U subframe) in subframe 7 correspondingto a prohibited subframe (N subframe) in subframe 7. Subframes 1-6 aredynamically (adaptively) assigned as either protected subframes (AU),prohibited subframes (AN), and common subframes (AC). During thedynamically assigned common subframes (AC) in subframes 5 and 6, boththe femto eNodeB and the macro eNodeB may transmit data.

Protected subframes (such as U/AU subframes) have reduced interferenceand a high channel quality because aggressor eNodeBs are prohibited fromtransmitting. Prohibited subframes (such as N/AN subframes) have no datatransmission to allow victim eNodeBs to transmit data with lowinterference levels. Common subframes (such as C/AC subframes) have achannel quality dependent on the number of neighbor eNodeBs transmittingdata. For example, if neighbor eNodeBs are transmitting data on thecommon subframes, the channel quality of the common subframes may belower than the protected subframes. Channel quality on common subframesmay also be lower for extended boundary area (EBA) UEs strongly affectedby aggressor eNodeBs. An EBA UE may belong to a first eNodeB but also belocated in the coverage area of a second eNodeB. For example, a UEcommunicating with a macro eNodeB that is near the range limit of afemto eNodeB coverage is an EBA UE.

In order to properly implement and maintain eICIC an eNodeB regularlymonitors the interference experienced in different subframe types by thevarious UEs it serves. That is, the eNodeB distinguishes interference onclean subframes, unclean subframe, common subframes, etc. However,legacy UEs can only monitor CQI generally, and cannot distinguishbetween different sets of subframes. Furthermore, more conventional UEscan only monitor two subframe types.

The channel quality indicator (CQI) may be different for differentsubframe types. For example, the CQI of a protected subframe may be muchhigher than the CQI of a common subframe. Typically, when schedulingsubframes, an eNodeB knows the correct CQI for each subframe consideredfor scheduling. For example, if an eNodeB is scheduling a commonsubframe, the eNodeB does not use the CQI for a protected subframe,because the CQI of the protected subframe is too optimistic. Althoughthe following description is with respect to CQI, it is noted that anytype of channel quality estimates are contemplated to be within thescope of the present disclosure.

New UEs may be adapted to measure CQI of multiple subframe types. Oneaspect of the present disclosure implements CQI reporting in both legacyUEs and newer UEs such that UEs may report CQI for subframes withdifferent interference levels using a single CQI subframe measurementassignment.

An eNodeB can broadcast common reference signals (CRS) for use by UEs toacquire the eNodeB, perform downlink CQI measurements, and performdownlink channel estimation. Newer UEs typically have a referencesignal-interference cancellation (RS-IC) capability allowing a newer UEto identify overlapping CRSs. However, to enable legacy UEs to functionin a cell, eNodeBs may be designed to prevent overlapping CRS. Forexample, when multiple different power class eNodeBs are present in acell, the CRS is offset such that the CRS of different eNodeBs does notcollide. In particular, in LTE, there are three available CRS offsets(assuming two transmission antennas at the eNodeB) and each eNodeB isassigned a different CRS offset. Alternately, assuming one transmissionantenna at the eNodeB, there are six different CRS offsets.

When the UE performs CQI measurements during the clean frames, the CQImeasurements tend to be higher because the aggressor eNodeBs are silent.However, a CQI measurement performed by the UE on an unclean subframemay be lower than that of a clean subframe. For example, if theaggressor eNodeB is transmitting during the unclean subframe, the CQI ofthe common subframe may be low. However, if the aggressor eNodeB is nottransmitting during the unclean subframe, the CQI may be high. The CQImay be correlated to the downlink buffer of the aggressor eNodeB. Forexample, if the downlink buffer of the aggressor eNodeB is full, the CQImay be low, but if the downlink buffer of the aggressor eNodeB is empty,the CQI may be high.

The subframe assignments may be correlated to interference patterns incells because the subframe assignments are used to coordinateinterference between eNodeBs in a cell. Subframe assignments, and thus,interference patterns, in cells repeat periodically. For example, insome cells the interference pattern repeats every eight milliseconds.

Additionally, providing a reporting periodicity that is a multiple ofthe periodicity of assignments in a cell would result in only a singlesubframe type (clean or unclean) being measured and reported through CQImeasurements to the eNodeB. Whether a clean or unclean subframe ismeasured by the UE's CQI measurement in this case depends on thesubframe offset indicated to the UE through a radio resourceconfiguration (RRC) message.

In one aspect, a UE may be directed to provide CQI measurements at aperiodic interval that is not a multiple of the periodicity ofinterference patterns in the cell. For example, in the case theinterference pattern periodicity is 8 milliseconds, the CQI measurementsmay occur periodically at any interval other than 8 milliseconds. Forexample, the CQI measurement periodicity may be selected as 10milliseconds.

FIG. 6 is a block diagram illustrating the CQI reporting periodaccording to one aspect of the disclosure. Each interference patternperiod is illustrated as eight subframes. Thus, the subframe typeassignment repeats each eight subframes. Each CQI reporting period isillustrated as 10 subframes. Thus, a UE performs CQI measurement andreporting at subframe 0 of the first interference pattern period,subframe 2 of the second interference pattern period, and subframe 4 ofthe third interference pattern period. In this example, the respectivesubframe types for the CQI measurements and reporting are a protectedsubframe (U subframe), common subframe (AC subframe), and prohibitedsubframe (N subframe).

In one aspect, a method 703 for measuring CQI is illustrated in FIG. 7C.At block 730, a UE is directed to establish a CQI measurement period atintervals that are not a multiple of the periodicity of interferencepatterns in the cell. At block 732, CQI is measured and reported inaccordance with the established CQI measurement period.

The measurement period can be based on a prime number, such as five. Ifthe interference period is eight, a measurement period of five ensuresthat each type of subframe (e.g., clean and unclean) is visited within40 ms. A forty millisecond periodicity of CQI reports may beinsufficient to provide the eNodeB with up-to-date information in somesituations such as, for example, when subframes are dynamically assignedor UEs are moving at high speeds.

When the CQI reporting periodicity is selected to have a differentlength than the interference pattern periodicity, the UE may visitdifferent interlaces. As long as the different interlaces include bothclean and unclean subframes, the UE performs CQI measurements on bothclean and unclean subframes.

After the UE reports the CQI measurements to a serving eNodeB, theeNodeB scheduler has up-to-date information regarding both clean andunclean subframes. Because the eNodeB knows the subframe assignments,the eNodeB may determine the subframe type assigned to each CQImeasurement without the UE knowing the subframe type being measured.According to one aspect, the eNodeB maintains two CQI backoff loops fortracking CQI measurements. Based on the subframe assignment, the eNodeBcan feed the incoming CQI reports to one of the multiple CQI backoffloops. For example, the eNodeB may manage two CQI backoff loopscorresponding to a clean CQI subframe loop and an unclean CQI subframeloop. If the periodicity selected for CQI measurements does not obtainmeasurements of clean and unclean subframes, the eNodeB may instruct theUE to select a new periodicity or offset through RRC messages.

According to another aspect, CQI reporting may be performed forindividual frequency subbands when frequency division multiplexing (FDM)is occurring. The UEs, including legacy UEs, may be instructed by aneNodeB to perform frequency domain CQI reporting. In frequency domainCQI reporting, the UE reports a CQI measurement of a subframe for aparticular frequency subband. The eNodeB may instruct the UE on thenumber of frequency subbands and which frequency subbands on which toperform CQI measurements through radio resource control (RRC) messaging.Frequency selection of CQI measurements in different subbands allows theeNodeB to use a schedule that takes into consideration informationregarding the subbands.

In one aspect, the aggressor eNodeB determines a particular subframe inwhich the UE served by a victim base station will perform a CQImeasurement. The determination may be based upon a transmission from thesecond base station that specifically identifies the subframe for CQImeasurement. Optionally, the aggressor and victim base stations maynegotiate over a backhaul to identify the particular subframe for CQImeasurement. Further, a predetermined rule may identify the particularsubframe.

When a CQI measurement is performed on a clean subframe, all of thesubbands may have a high CQI. A CQI for an unclean subframe may bemeasured by using an eNodeB to simulate unclean subframes. For example,referring to FIG. 8A, an aggressor eNodeB may transmit dummy data onresource elements (REs) 810 used by a victim eNodeB's CRS on a specificsubband. The transmitted dummy data generates interference on thefrequency subband. According to one aspect, the dummy data arepseudo-random signals (i.e., noise) not directed to any specific UE. Ifthe transmission power spectral density (TX PSD) of the dummy data isthe same as (or similar to) the TX PSD of data during real datatransmission, then the CQI measured by a UE on the subband isapproximately equal to the CQI of an unclean subframe when the aggressoreNodeB has full downlink buffers.

The measured CQI of the unclean subframe on the subband may be lowerthan the measured CQI of a clean subframe. The number of resourceelements jammed by an aggressor eNodeB may be a function of the amountof data in the downlink buffer of the aggressor eNodeB. An aggressoreNodeB may mimic a partially loaded system, by transmitting interferingdummy data on only some resource elements. For example, if the eNodeBknows the system is only 50% loaded, then the eNodeB would only pollute50% of the resource elements. In another configuration, the eNodeBexamines a history of loading to estimate the current load.

According to another aspect, a frequency subband may be set aside as aspecial frequency subband. For example, the special frequency subbandmay be a reserved frequency subband where resource elements used by avictim eNodeB's CRS are not used for data transmission by the aggressoreNodeB.

Alternatively, the special frequency subband may be used for datatransmission but the symbols in the reserved resource elements arepunctured. For example, referring to FIG. 8B, data transmission may takeplace on the frequency subbands as long as no symbols are transmitted onresource elements belonging to the CRS of a victim eNodeB. The resourceelements 820 of the aggressor eNodeB are punctured to allow fortransmission of resource elements 822 reserved for the victim eNodeB.The CQI measurements on the reserved frequency subband are comparable toclean subframe measurements because of the absence of interference onthe CRS resource elements. Additionally, a partially loaded system maybe simulated by puncturing some of the CRS tones.

The special frequency subband may be, for example, statically assigned,negotiated between eNodeBs, or follow a hopping pattern according to apseudo-random (but deterministically known) pattern. According to oneaspect, the special frequency subband is a hopping subband designed suchthat CQI reports of both clean and unclean subframes are periodicallyreceived by the eNodeB for all frequency subbands.

When CQI reporting is performed on frequency subbands, the eNodeB mayreceive CQI reports for both clean and unclean subframes in the samereport. For example, the CQI report may include information for a cleansubframe on a first frequency subband and an unclean subframe on asecond frequency subband. In one aspect, the clean and unclean subbandsalternate in the time domain. When scheduling subframes, an eNodeB mayuse CQI reports from clean subframes across the entire bandwidth (allfrequency subbands) and unclean subframes across the entire bandwidth.

According to one aspect, when deriving the CQI reports, the eNodeB mayestimate, through blind detection, which frequency subband was cleanedand/or which frequency subband was jammed, in case this information isnot available. Alternatively, this information is negotiated between theeNodeBs.

The methods described above for performing CQI measurements of clean andunclean subframes allow both legacy UEs and newer UEs to provide CQIreports to the eNodeB for multiple types of subframes. Moreover, noadditional information is transferred to the UE for making the CQImeasurements beyond the information normally provided to the UE throughradio resource control signaling. That is, no new periodicities and noindication of which subframe to use for clean subframe and uncleansubframe CQI measurements is provided to the UE. Moreover, no newmethods for jointly reporting different types of subframes are added tothe UE.

FIG. 7A illustrates a method 701 for estimating channel quality by afirst base station, the aggressor base station, in a wireless network.In block 710, the first base station determines a subframe in which a UEserved by a second base station, the victim base station, will perform achannel measurement. In block 712, the first base station affects thechannel measurement by either (1) transmitting dummy signals over CRStones corresponding to the second base station on a first selectedsubband during the subframe or (2) puncturing transmission during theCRS tones corresponding to the second base station over a secondselected subband during the subframe (e.g., over the backhaul or using awireless interface).

FIG. 7B illustrates a method 702 for channel quality estimation in awireless network. In block 720, a victim base station indicates to auser equipment (UE) to perform channel quality measurements for at leasttwo subbands in a subframe. The base station receives a first channelquality report and a second channel quality report from a UE in block722. The first channel quality report includes a first channelmeasurement of a first subband and the second channel quality reportincludes a second channel measurement of a second subband. In block 724,the base station determines separate channel measurements for clean andunclean subframes based on the first and second reports.

This description may apply to ARPI and may also apply to semi-staticassignments without dynamic subframe assignment. Although the precedingdescription was with respect to clean and unclean subframes, other typesof subframes are also contemplated, e.g., dynamic clean, dynamicunclean, special, etc.

In one configuration, an aggressor eNodeB 110 is configured for wirelesscommunication including means for determining. In one aspect, thedetermining means may be the controller/processor 440 and memory 442configured to perform the functions recited by the determining means.The eNodeB 110 is also configured to include a means for affecting thechannel quality measurement. In one aspect, the affecting means may bethe controller/processor 440, memory 442, transmit processor 420,modulators 432 a-t and antenna 434 a-t configured to perform thefunctions recited by the affecting means. In another aspect, theaforementioned means may be a module or any apparatus configured toperform the functions recited by the aforementioned means.

In one configuration, a victim eNodeB 110 is configured for wirelesscommunication including means for indicating. In one aspect, theindicating means may be the controller processor 440, memory 442,transmit processor 420, modulators 432 a-t and antenna 434 a-tconfigured to perform the functions recited by the indicating means. TheeNodeB 110 is also configured to include a means for receiving. In oneaspect, the receiving means may be the receive processor 438,demodulators 432 a-t, controller/processor 440 and antenna 434 a-tconfigured to perform the functions recited by the receiving means. TheeNodeB 110 is also configured to include a means for determining. In oneaspect, the determining means may be the controller/processor 440 andmemory 442 configured to perform the functions recited by thedetermining means. In another aspect, the aforementioned means may be amodule or any apparatus configured to perform the functions recited bythe aforementioned means.

Those of skill would further appreciate that the various illustrativelogical blocks, modules, circuits, and algorithm steps described inconnection with the disclosure herein may be implemented as electronichardware, computer software, or combinations of both. To clearlyillustrate this interchangeability of hardware and software, variousillustrative components, blocks, modules, circuits, and steps have beendescribed above generally in terms of their functionality. Whether suchfunctionality is implemented as hardware or software depends upon theparticular application and design constraints imposed on the overallsystem. Skilled artisans may implement the described functionality invarying ways for each particular application, but such implementationdecisions should not be interpreted as causing a departure from thescope of the present disclosure.

The various illustrative logical blocks, modules, and circuits describedin connection with the disclosure herein may be implemented or performedwith a general-purpose processor, a digital signal processor (DSP), anapplication specific integrated circuit (ASIC), a field programmablegate array (FPGA) or other programmable logic device, discrete gate ortransistor logic, discrete hardware components, or any combinationthereof designed to perform the functions described herein. Ageneral-purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

The steps of a method or algorithm described in connection with thedisclosure herein may be embodied directly in hardware, in a softwaremodule executed by a processor, or in a combination of the two. Asoftware module may reside in RAM memory, flash memory, ROM memory,EPROM memory, EEPROM memory, registers, hard disk, a removable disk, aCD-ROM, or any other form of storage medium known in the art. Anexemplary storage medium is coupled to the processor such that theprocessor can read information from, and write information to, thestorage medium. In the alternative, the storage medium may be integralto the processor. The processor and the storage medium may reside in anASIC. The ASIC may reside in a user terminal. In the alternative, theprocessor and the storage medium may reside as discrete components in auser terminal.

In one or more exemplary designs, the functions described may beimplemented in hardware, software, firmware, or any combination thereof.If implemented in software, the functions may be stored on ortransmitted over as one or more instructions or code on acomputer-readable medium. Computer-readable media includes both computerstorage media and communication media including any medium thatfacilitates transfer of a computer program from one place to another. Astorage media may be any available media that can be accessed by ageneral purpose or special purpose computer. By way of example, and notlimitation, such computer-readable media can comprise RAM, ROM, EEPROM,CD-ROM or other optical disk storage, magnetic disk storage or othermagnetic storage devices, or any other medium that can be used to carryor store desired program code means in the form of instructions or datastructures and that can be accessed by a general-purpose orspecial-purpose computer, or a general-purpose or special-purposeprocessor. Also, any connection is properly termed a computer-readablemedium. For example, if the software is transmitted from a website,server, or other remote source using a coaxial cable, fiber optic cable,twisted pair, digital subscriber line (DSL), or wireless technologiessuch as infrared, radio, and microwave, then the coaxial cable, fiberoptic cable, twisted pair, DSL, or wireless technologies such asinfrared, radio, and microwave are included in the definition of medium.Disk and disc, as used herein, includes compact disc (CD), laser disc,optical disc, digital versatile disc (DVD), floppy disk and Blu-ray discwhere disks usually reproduce data magnetically, while discs reproducedata optically with lasers. Combinations of the above should also beincluded within the scope of computer-readable media.

The previous description of the disclosure is provided to enable anyperson skilled in the art to make or use the disclosure. Variousmodifications to the disclosure will be readily apparent to thoseskilled in the art, and the generic principles defined herein may beapplied to other variations without departing from the spirit or scopeof the disclosure. Thus, the disclosure is not intended to be limited tothe examples and designs described herein but is to be accorded thewidest scope consistent with the principles and novel features disclosedherein.

What is claimed is:
 1. A method for channel quality estimation in awireless network, comprising: indicating, to a user equipment (UE), toperform a plurality of channel quality measurements for at least twosubbands in a subframe; receiving, from the UE, a first channel qualityreport including a first channel quality measurement of a first subbandand a second channel quality report including a second channel qualitymeasurement of a second subband; and determining separate channelquality measurements for a first subframe type and a second subframetype based on the first and second reports.
 2. The method of claim 1,further comprising: receiving, from the UE, a third channel qualityreport including a third channel quality measurement of a third subband;and determining a channel quality measurement for a third subframe typebased on the third report.
 3. The method of claim 1, in which the firstsubframe type is a clean subframe and the second subframe type is anunclean subframe.
 4. The method of claim 1, further comprisingidentifying a subframe in which the UE served by a second base stationwill perform a channel quality measurement, in which the identifyingcomprises at least one of: negotiating over a backhaul with the secondbase station to identify the subframe; and identifying the subframeaccording to a predetermined rule.
 5. The method of claim 1, in whichthe first and second subbands are at least one of: statically assigned,semi-statically negotiated among involved base stations, and dynamicallychanging following predefined hopping patterns.
 6. An apparatus forwireless communication, comprising: means for indicating, to a userequipment (UE), to perform a plurality of channel quality measurementsfor at least two subbands in a subframe; means for receiving, from theUE, a first channel quality report including a first channel qualitymeasurement of a first subband and a second channel quality reportincluding a second channel quality measurement of a second subband; andmeans for determining separate channel quality measurements for a firstsubframe type and a second subframe type based on the first and secondreports.
 7. A computer program product for wireless communication in awireless network, comprising: a non-transitory computer-readable mediumhaving non-transitory program code recorded thereon, the program codecomprising: program code to indicate, to a user equipment (UE), toperform a plurality of channel quality measurements for at least twosubbands in a subframe; program code to receive, from the UE, a firstchannel quality report including a first channel quality measurement ofa first subband and a second channel quality report including a secondchannel quality measurement of a second subband; and program code todetermine separate channel quality measurements for a first subframetype and a second subframe type based on the first and second reports.8. An apparatus for wireless communication, comprising: a memory; and atleast one processor coupled to the memory, the at least one processorbeing configured: to indicate, to a user equipment (UE), to perform aplurality of channel quality measurements for at least two subbands in asubframe; to receive, from the UE, a first channel quality reportincluding a first channel quality measurement of a first subband and asecond channel quality report including a second channel qualitymeasurement of a second subband; and to determine separate channelquality measurements for a first subframe type and a second subframetype based on the first and second reports.
 9. The apparatus of claim 8,in which the processor is further configured: to receive, from the UE, athird channel quality report including a third channel qualitymeasurement of a third subband; and to determine a channel qualitymeasurement for a third subframe type based on the third report.
 10. Theapparatus of claim 8, in which the first subframe type is a cleansubframe and the second subframe type is an unclean subframe.
 11. Theapparatus of claim 8, in which the processor is further configured toperform at least one of: negotiating over a backhaul with the secondbase station to identify the subframe; and identifying the subframeaccording to a predetermined rule.
 12. The apparatus of claim 8, inwhich the first and second subbands are at least one of: staticallyassigned, semi-statically negotiated among involved base stations, anddynamically changing following predefined hopping patterns.